1. Field of the Invention
The present invention generally relates to ophthalmic lenses. More specifically, the present invention provides improved progressive addition lenses (PALs).
2. Background Art
Conventional PALs are typically designed to require the resulting vision zones to be as wide as possible and to be substantially free of unwanted astigmatism. Requiring the vision zones to be free of astigmatism fails to consider the adverse impact on visual comfort caused by rapidly changing the magnitude of oblique astigmatism that consequently builds up on both sides of the channel and the viewing zones. This rapid buildup of astigmatism can also adversely impact the width of the distance vision zone of the resulting PAL. Accordingly, what is needed is an ophthalmic lens design that bases viewing zone widths and acceptable levels of astigmatism on actual wearer use and comfort so as to achieve improved PAL designs.